Antibacterial photodynamic therapy in dermatology

Abstract

Photodynamic therapy (PDT) appears to be endowed with several favourable features for the treatment of localized microbial infections, especially after the advent of cationic photosensitising agents (phenothiazines, meso-substituted porphyrins, polylysine-bound chlorins) which properly interact with the outer wall at the surface of several types of bacterial and yeast cells, increase their permeability, and allow significant amounts of photosensitizer to be accumulated at the level of the cytoplasmic membrane. These photosensitisers are characterized by a broad spectrum of activity, being effective toward both wild strain and antibiotic-resistant gram-positive and gram-negative bacteria and yeasts. In general, extensive eradication of pathogens can be achieved under mild irradiation conditions, such as short incubation times and low fluence-rates, which guarantees a high degree of selectivity in comparison with the main constituents of host tissues, such as keratinocytes and fibroblasts. Moreover, the photosensitised inactivation of microorganisms is typically a multi-target process; as a consequence, the selection of photoresistant microbial strains is very unlikely and has not been experimentally observed so far. Possible initial targets of antimicrobial PDT applications include periodontal diseases, impetigo, atopic dermatitis, acne vulgaris, infected wounds, and superinfected posriatic plaques.

A comparative in vitro photoinactivation study of clinical isolates of multidrug-resistant pathogens

“…They possess a slightly negatively charged surface and are also sensitive to cationic PS, although anionic and neutral PSs can also be used to eradicate Gram-positive bacteria. 5,6,19 The susceptibility differences observed between E. coli and S. aureus and pL-ce6 and TBO may be due to their different chemical properties, as indicated by Demidova and Hamblin et al 12 Although both pL-ce6 and TBO are cationic, pL-ce6 possesses a relatively larger molecular weight and the molecule has a greater number of potentially positively charged groups than TBO. The large molecular weight of pL-ce6 may not facilitate its ready penetration into the cell wall of the Gram-positive S. aureus leading to photodestruction.…”

Photobiological characteristics of chlorophyll a derivatives as microbial PDT agents

“…33 However, the cationic chlorins appear to be quite effective for such microorganisms. [34][35][36] The PDT inactivation experiments with Candida albicans were also performed to evaluate the effect of these PSs in a fungus cell, as it has a different cell wall when compared to bacteria. 37 We evaluated the PDT activity of both PSs at 20 and 30 μg mL Previous studies have reported the inactivation of Candida albicans with PDT using Photogem, 37 which presents the same complete inhibition with 50 μg mL −1 and a fluence of…”

Photoantimicrobials and Photodynamic Antimicrobial Therapy in Search of Antibiotics

“…Penisilinin 1928'de Alexander Fleming tarafından keşfiyle FDAT eski önemini kaybetmiştir. Ancak, lokalize enfeksiyonlarda sistemik bir tedavinin gerekli olmaması ve antibiyotiklere karşı mikroorganizmaların geliştirmiş olduğu direnç sorunu FDAT'yi yeniden gündeme getirmiştir (30,46,47) . Daha sonraki yıllarda FDAT ile ilgili çalışmalar hız kazanmış ve fotofrin (porfimer sodyum) 1993'te Kanada'da, 1995 yılında ise diğer ülkeler de dahil olmak üzere Amerika'da kullanıma girmiş ve Amerika'da Food and Drug Administration'dan (FDA) klinik kullanım izni almıştır (1,3) .…”

“…Daha sonraki yıllarda FDAT ile ilgili çalışmalar hız kazanmış ve fotofrin (porfimer sodyum) 1993'te Kanada'da, 1995 yılında ise diğer ülkeler de dahil olmak üzere Amerika'da kullanıma girmiş ve Amerika'da Food and Drug Administration'dan (FDA) klinik kullanım izni almıştır (1,3) . Fotofrinin klinik kullanıma girmesiyle birlikte özellikle son 20 yılda enfeksiyon hastalıklarıyla mücadele-de alternatif bir yaklaşım olarak FDAT ile ilgili çalışmaların sayısında artış olmuş-tur (3,30,38,53) .…”

“…Bu nedenle, mikroorganizmaların hücre dışı yapılarındaki farklı-lıklar seçilen FS'i spesifik kılmaktadır (18,30,34) . Gram negatif ve Gram pozitif bakterilerin hücre duvarı yapısındaki farklılıklar, bu organizmaların farklı elektriksel yükteki FS ile farklı etkileşimlerin oluşmasına neden olmaktadır (18,48) .…”